As an article of commerce anhydrous AlF.sub.3 is a white crystalline solid which sublimes at 1290.degree. C./760 mm. It is most conveniently prepared by fluoriding Al.sub.2 O.sub.3 with gaseous or aqueous HF (1) EQU Al.sub.2 O.sub.3 +6 HF.fwdarw.2AlF.sub.3 +3H.sub.2 O (1)
or by allowing an aluminum hydrate to react with ammonium bifluoride (2) EQU Al(OH).sub.3 +3NH.sub.4 HF.sub.2 .fwdarw.AlF.sub.3 +3NH.sub.4 F+3H.sub.2 O (2)
in solution or in the solid state. The reactions summarized in equations 1 and 2 are normally conducted at temperatures of about 600.degree. C. and higher. The anhydrous AlF.sub.3 thus produced is typically in the form of a very fine powder. Detailed discussions of the common commercial methods of AlF.sub.3 preparation may be found in either Kirk-Othner Encyclopedia of Chemical Technology, Second Edition, Vol. 9, Wiley, New York, pgs. 527-547; or G. N. Kannan, Indian Chem. J. 4, 22, 1969. Commercially available AlF.sub.3 ranges from 60-90% AlF.sub.3, the major impurities being H.sub.2 O, Al.sub.2 O.sub.3 and mixed aluminum hydroxyfluorides. Commercially available AlF.sub.3 is of limited value in catalytic operations since the fine powder cannot be satisfactorily compacted or extruded into self-supporting pellets. Also in many catalytic applications unreacted Al.sub.2 O.sub.3 cannot be tolerated.